Various kinds of microscopes are utilized for magnifying observation of an eye in the field of ophthalmology. Examples of such ophthalmologic microscopes include slit lamp microscopes and surgical microscopes. There are ophthalmologic microscopes that include an image sensor for imaging an eye, and those that include a binocular optical system that provides binocular disparity for stereoscopic observation.
The ophthalmologic microscopes may be used in combination with another ophthalmologic apparatus. For example, a system is known in which an optical coherence tomography (OCT, hereinafter) apparatus or a laser treatment apparatus is combined with an ophthalmologic microscope. The OCT apparatus is utilized for, for example, acquiring cross sectional images of an eye, acquiring three dimensional images of an eye, measuring the sizes of ocular tissues (e.g., the thickness of the retina), and acquiring functional information on an eye (e.g., the blood flow information). The laser treatment apparatus is utilized for, for example, laser photocoagulation treatment of the retina, the corner angle, etc.
[Patent Document 1] U.S. Pat. No. 8,049,873.
The conventional ophthalmologic microscope system includes a Galilean stereo microscope. The Galilean stereo microscope is characterized in that the binocular optical system has a common objective lens and that the left and right optical axes of the binocular optical system are parallel to each other. The Galilean stereo microscope has an advantage of being able to combine other optical systems and optical elements easily. On the other hand, since it is necessary to use an objective lens with a large diameter, the Galilean stereo microscope has a disadvantage that the degree of flexibility in optical design or mechanism design is limited.
When another ophthalmologic apparatus such as an OCT apparatus is used in combination with an ophthalmologic microscope, it is necessary to arrange the optical path of the light projected by the OCT apparatus while making a way around the optical path of the binocular optical system, thereby making it difficult to project the light from the OCT apparatus onto the eye from the direction perpendicular to the eye. When the light from the OCT apparatus enters the eye from an oblique direction, the iris may cause the vignetting of the light or its returning light, and this may lead to a problem that the performance of the OCT apparatus cannot be sufficiently exerted.